Monday, September 29, 2014

A special report "Explaining extreme events of 2013 from a climate perspective" has been published today in the Bulletin of the American Meteorological Society. The authors claim to "link" some extreme heat waves to anthropogenic global warming, but not other extreme weather including droughts, heavy rain, and storms.

"In this paper, 20 different research groups explored the causes of 16 different events that occurred in 2013.The findings indicate that human-caused climate change greatly increased the risk for the extreme heat waves assessed in this report. How human influence affected other types of events such as droughts, heavy rain events, and storms was less clear, indicating that natural variability likely played a much larger role in these extremes."

Thus, as noted today on twitter by Dr. Roger Pielke Jr, "the bottom line on this new NOAA special report: If you are attributing any extreme other than heat waves to Anthropogenic Climate Change, you are on weak (or worse) scientific ground."

Further, is it possible to determine how much warming to attribute to natural warming recovery since the Little Ice Age vs. possible anthropogenic change? This paper cites the IPCC report and claim that "most" of the warming since 1950 is anthropogenic. However, this is the false attribution assumption and is thus used as the underlying basis for blaming some of the heat waves of 2013 on man-made emissions of CO2. How can they then explain why the most extreme US heat waves by far occurred during the low-CO2 1930's?

Of course, none of this science stops our favorite Associated Press propagandist Seth Borenstein from spinning this study as

WASHINGTON -- Scientists looking at 16 cases of wild weather around the world last year see the fingerprints of man-made global warming on more than half of them.

Researchers found that climate change increased the odds of nine extremes: Heat waves in Australia, Europe, China, Japan and Korea, intense rain in parts of the United States and India, and severe droughts in California and New Zealand.

Scientists couldn't find a global warming link to an early South Dakota blizzard, freak storms in Germany and the Pyrenees, heavy rain in Colorado, southern and central Europe, and a cold British spring....

By Stephanie C. Herring, Martin P. Hoerling, Thomas C. Peterson, and Peter A. StottABSTRACT:Attribution of extreme events is a challenging scienceand one that is currently undergoing considerable evolution.In this paper, 20 different research groups exploredthe causes of 16 different events that occurred in 2013.The findings indicate that human-caused climate changegreatly increased the risk for the extreme heat wavesassessed in this report. How human influence affectedother types of events such as droughts, heavy rain events,and storms was less clear, indicating that natural variabilitylikely played a much larger role in these extremes.Multiple groups chose to look at both the Australian heatwaves and the California drought, providing an opportunityto compare and contrast the strengths and weaknessesof various methodologies. There was considerableagreement about the role anthropogenic climate changeplayed in the events between the different assessments.This year three analyses were of severe storms and nonefound an anthropogenic signal. However, attribution assessmentsof these types of events pose unique challengesdue to the often limited observational record. Whenhuman-influence for an event is not identified with thescientific tools available to us today, this means that ifthere is a human contribution, it cannot be distinguishedfrom natural climate variability.